The present invention relates to a technique of liquid crystal display(LCD) capable of preventing a color shift.
In general, an IPS-LCD(In-Plane Switching Liquid Crystal Display) for improving a narrow viewing angle of a TN-LCD (Twisted Nematic Liquid Crystal Display), suggested by Hitachi Cooperation of Japan, has electrodes 2a and 2b disposed on a lower substrate 1, which drive liquid crystal molecule 3a. Therefore, there is generated an electric field parallel to the lower substrates, as shown in FIG. 1.
The IPS-LCD has some problems and one of them is the color shift which will be detailed described. Before the electric field is formed between electrodes, the molecules 3a are arranged along a direction of an alignment layer(not shown) formed on the lower substrate. When the electric field is generated, the liquid crystal molecules rotate and thus are arranged along the electric field F. Major axis of the liquid crystal molecules which have positive dielectric anisotropy is parallel to the electric field while minor axis of the liquid crystal molecules which have negative dielectric anisotropy is parallel to the electric field. Since shape of the liquid crystal molecule is rod form and the length of major axis is different from that of the minor axis, there is an optical anisotropy. Accordingly, there is generated a color variation in the screen of the LCD according to the viewing point. That is, after the electric field is generated, at Y direction the minor axis of the liquid crystal molecule is observed, the screen of the LCD takes a blue color with shorter wavelength than white. At X direction the major axis of the liquid crystal molecule is observed, the screen of the LCD takes a yellow color with longer wavelength than white. Therefore, the picture quality of the LCD is degraded.
Accordingly, an aim of a present invention is to prevent a color shift in an IPS-LCD, thus improving a picture quality.
In order to accomplish the aim of the present invention, a distance between a pixel electrode and a counter electrode is different among unit pixel space at a portion adjacent to a data bus line and a portion near a center of the unit pixel space such that an intensity of an electric field formed between the pixel electrode and the counter electrode is different at the portion adjacent to the data bus line and the portion near the center of the unit pixel space.
In detail, the LCD of the present invention has a gate bus line arranged in a first direction on a substrate; a data bus line arranged in a second direction substantially perpendicular to the first direction on the substrate, the data bus line defining a space for an unit pixel of the LCD together with the gate bus line; a counter electrode having a first part formed in the unit pixel space and extended in the second direction, the first part being at least three; and a pixel electrode having a second part extended between the first parts of the counter electrode and disposed in the second direction, the second part being at least two and slanting to one side of adjacent first parts thereto. In an embodiment, the counter electrode further comprises a pair of third parts for connecting ends of the first parts of the counter electrode, the third part extended in the first direction and being a rectangular frame. In another embodiment, the pixel electrode further comprises a pair of fourth parts for connecting ends of the second parts, the fourth part extended in the first direction and overlapped with the third part. In one embodiment, the second part is slanted to the first part adjacent to the data bus line among at least three-first parts and in another embodiment the second part is slanted to the first part adjacent to the center of the unit pixel space among at least three-first parts.
In another view, the LCD comprises an upper substrate and a lower substrate opposite thereto, liquid crystal molecules interposed therebetween; a gate bus line arranged in a first direction on the lower substrate; a data bus line arranged in a second direction substantially perpendicular to the first direction on the substrate, the data bus line defining a space for an unit pixel of the LCD together with the gate bus line; a counter electrode formed in the unit pixel space of the LCD and a rectangular frame shape, the counter electrode having at least one bar for dividing an inside of the frame; and a pixel electrode formed in the unit pixel space where the counter electrode is formed, the pixel electrode having a first part and second part each overlapped with one pair of opposite sides of the frame and a third part for connecting the first part and the second part, the third part being at least two and parallel to the bar of the counter electrode, the third part, between the bar of the counter and the other pair of opposite sides of the frame, slanting to one side among them. Here, the bar of the counter electrode and the third part of the pixel electrode are parallel to the data bus line. The liquid crystal molecule has a positive or a negative dielectric anisotropy. The product of a distance between the upper substrate and the lower substrate and an index of refraction anisotropy is about 0.2 xcexcm to about 0.6 xcexcm.
From the above mentioned LCD, an electric field of a certain portion among the unit pixel space is stronger than that of other portion, so a rotation angle of liquid crystal molecule is different at these portions. Accordingly, an optical isotropy of liquid crystal is compensated and thus the color shift is prevented.